In children withi hiearing loss (CHL), the presence of vestibular loss may result in gross motor developmental delay and reduced visual acuity, requiring additional habilitation. However, vestibular testing is not routine in the pediatric population, and vestibular habilitation is seldom considered for CHL. The longterm goal of this research program is to diagnose and then minimize the impact of vestibular loss in CHL. As a first step, the objectives in the present proposal are to characterize vestibular function in CHL, and investigate the effect of vestibular loss on static (head stable) and dynamic (head in motion) visual acuity in these children. The central hypothesis is that both static visual acuity (SVA) and dynamic visual acuity (DVA) are degraded in CHL with vestibular loss. This hypothesis is based on research in adults with vestibular loss, who experience reduced visual acuity with standing, walking and head movement, which impairs activities of daily living. The rationale for the proposed research is that reduced visual acuity, especially in the classroom, may impair academic success in CHL. Preliminary data obtained in our lab suggests that visual acuity is reduced in CHL. Two specific aims will be addressed in this proposal: 1) we will characterize vestibular loss in CHL, and 2) we will evaluate the effect of vestibular loss on SVA and DVA in these children. We will focus on CHL who use a cochlear implant (CI), who have increased risk of vestibular loss due to implantation and etiology of hearing loss. This provides a population of CHL with vestibular loss where visual acuity can be better studied. In Aim 1, a new approach for assessing semicircular-canal function that has been developed for use in adults will be evaluated in children. Additionally, the relationship between severity of vestibular loss and gross motor performance will be investigated. In Aim 2, SVA and DVA will be assessed while sitting and under increasing demands of maintaining upright stance. This work will provide new knowledge regarding the prevalence of vestibular loss and the extent to which vestibular loss affects visual acuity in CHL. This will further advance our understanding of the natural compensation process of vestibular loss in CHL and lead to further investigations regarding the identification, implications, and habilitation of vestibular loss in CHL.